test_webhook · Posteverywhere MCP: Risk & Policy

WHAT IT DOES

What test_webhook does on Posteverywhere

AI agents invoke test_webhook to trigger actions in Posteverywhere. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why test_webhook needs a policy

This tool triggers an external HTTP request to a webhook endpoint, which is an Execute-category action — it performs an outbound network operation with side effects (the receiving endpoint processes the ping). It does not create/modify persistent data (Write), nor is it destructive or financial.

From the tool's definition Send a synthetic test ping to a webhook URL... verify your endpoint receives the request and validates the HMAC signature

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

test_webhook Rate-limited

test_webhook stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "test_webhook": {
      "limits": [
        {
          "counter": "test_webhook_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Posteverywhere, so you can run agents against it safely.

FAQ

Questions about test_webhook

What does the test_webhook tool do? +

Send a synthetic test ping to a webhook URL on PostEverywhere so you can verify your endpoint receives the request and validates the HMAC signature. Returns the receiver\. It is categorised as a Execute tool in the Posteverywhere MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on test_webhook? +

Register the Posteverywhere MCP server in PolicyLayer and add a rule for test_webhook: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Posteverywhere. Nothing to install.

What risk level is test_webhook? +

test_webhook is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit test_webhook? +

Yes. Add a rate_limit block to the test_webhook rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block test_webhook completely? +

Set action: deny in the PolicyLayer policy for test_webhook. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides test_webhook? +

test_webhook is provided by the Posteverywhere MCP server (posteverywhere/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.